This application claims the priority of German Patent Application Serial No. 199 52 817.9, filed Nov. 2, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates to a reflector antenna with a stator portion and a rotor portion which is supported for rotation relative to the stator portion about a rotation axis, with a reflector secured to the rotor portion and connected by an electrical connection with the stator portion.
Reflector antennas of this type are used with increasing frequency on moveable vessels, such as ships, for receiving radio signals emitted by satellites. Until now, the electrical connection between the rotor portion and the stator portion has been unsatisfactory, since a fixed connecting cables could not be used between the rotor portion and the stator portion and the electrical antenna signals had to be transmitted instead from the rotor portion to the stator portion by using, for example slip rings. However, slip rings introduce noise in the transmission so that the transmitted signal tends not to be clear. Moreover, the wear of the slip rings strongly affects their performance as evidenced by an increase in the number of interfering signals. Arcing can also falsify the transmitted data, so that a clear reception can no longer be expected.
It is thus an object of the present invention to provide an improved reflector antenna, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved a reflector antenna that can transmit radio signals received by the reflector to the stator portion with as little loss and as much clarity as possible.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing the connection as a flexible connecting cable, wherein one end of the cable is attached to the rotor portion and the other end is attached to the stator portion. The end attached to the rotor portion does not move relative to the rotor portion, and the end is attached to the stator portion does not move relative to the stator portion. The ends face one another in the direction of the rotation axis and are connected through a segment of the connecting cables, the respective segment rotating with half the rotation speed of the rotor portion with the same rotation direction as the rotor portion.
Since the end of the connecting cables that is connected in this manner to the stator portion is tracking, the rotor portion can be connected to the stator portion by a flexible connecting cables. This flexible cables can be implemented as a shielded cables, thereby reducing the losses produced in the connecting cables. Accordingly, the received antenna power available at the output of the reflector antenna is maximized and becomes available in high quality, for example, for providing signals to monitors.
According to an embodiment of the invention, the rotatable segment of the connecting cables passes through a first guide disposed on a drive wheel that is driven with half the rotation speed of the rotor portion. The rotatable segment of connecting cables is connected to the stator portion before the connecting cables enters the guide, and is connected with the rotor portion after the connecting cables leaves the guide. The connecting cables rotates in the guide with half the rotation speed of the rotor portion. In this way, the desired rotation speed can be precisely maintained, eliminating mechanical stress in the connecting cables.
According to another embodiment of the invention, the rotatable segment of the connecting cables is guided through a channel of the drive wheel from the center of the drive wheel outwardly towards the circumference of the drive wheel. This arrangement of the drive channel not only reliably guides the rotatable segment of the connecting cables, but also guides the rotatable segment from the stator portion to the rotor portion with a curvature in conformance with design constraints.
According to another embodiment of the invention, the channel is formed as a bore which surrounds the rotatable segment of the connecting cables with ample clearance so that the connecting cables is movably supported in the bore. In this way, the rotatable segment of the connecting cables is not prevented from performing the necessary compensating motion in order to track the respective rotation of the rotor portion.
According to another embodiment of the invention, the rotatable segment of the connecting cables extends through a slot in the form of a channel that surrounds the connecting cables with ample clearance. The slot extends radially through the drive wheel. Such slot can be easily produced and can reliably guide the connecting cables.
According to another embodiment of the invention, the connecting cables includes another section that continuous from the rotatable segment in the direction of the rotor portion and passes through a guide tube. This section that extends into guide tube rotates with the rotor portion with the same rotation direction and the same rotation speed. The guide tube is hence rotatably coupled with the rotating portion. This produces a particularly space-saving arrangement of the connecting cables.
According to another embodiment of the invention, drive means are provided on the drive wheel for driving the rotor portion that rotates with twice the rotation speed of the drive wheel. In this way, the rotation speed of the rotor portion relative to that of the drive wheel can easily controlled without having to resort to complex drive assemblies.
According to another embodiment of the invention, the drive means are formed as a shaft that extends through the drive wheel parallel to the shaft of the drive wheel. Drive pinions mesh with teeth disposed on respective ends of the shaft that project from opposing surfaces of the drive wheel. The teeth are connected, on one hand, with the stator portion and, on the other hand, by another pinion with the rotor portion. The drive pinions increase the rotation speed by a ratio of 2:1 relative to the drive wheel. A shaft of this type which extends through the drive wheel with at least one pinion and a deflection pinion for reversing the rotation direction, represents a simple and therefore inexpensive gear that can maintain the ratio of the rotation speed of the rotor portion to the rotation speed of the connecting cables at a value of 2:1. By directly coupling the rotor portion to the drive wheel, the rotation speed ratio is held constant in each phase independent of the rotation speed of the drive wheel. The necessary drive means are inexpensive and can be easily assembled.
According to another embodiment of the invention, the rotor portion has a first motor that drives the rotor portion relative to the drive wheel. In addition, the drive wheel is driven by a second motor located on the stator portion. With the separate motor drive, the rotor portion and the drive wheel can be driven independently of one another, so that the drive wheel has exactly half the rotation speed of the rotor portion. Moreover, the motors can be easily electrically controlled, thereby eliminating complicated and expensive mechanical controls.
According to another embodiment of the invention, the two motors are coupled by suitable gears to the rotor portion and the drive wheel, respectively, with the rotor portion being controlled relative to the drive wheel with a ratio of 2:1. Such gears are simple and can be manufactured relatively inexpensively. The rotation speed of the rotor portion can be selected to be exactly half the rotation speed of the drive wheel.
According to another embodiment of the invention, the two motors are coupled to the drive wheel and the rotor portion, respectively, by toothed belts. Toothed gear drives of this type are particularly simple and easy to maintain. They can also be quickly exchanged and allow precise control of the drive wheel relative to the rotor portion.
According to another embodiment of the invention, both sides of the toothed belts have teeth, wherein the teeth on one side mesh with the teeth of a drive pinion and the teeth on the other side mesh with the teeth of the rotor portion. By suitably sizing the teeth disposed on the respective toothed belts, a single toothed belt is sufficient to drive the rotor portion in the same rotation direction as the drive wheel with twice the rotation speed.
According to another embodiment of the invention, the toothed belt engages with the teeth of the rotor portion and after one turn, engages with the teeth of the drive wheel. In this way, two different drive means, i.e., the drive wheel and the rotor portion, respectively, can be driven by deflecting the toothed belt.
According to another embodiment of the invention, the stator portion as well as the rotor portion include a section formed as a hollow cylinder. Teeth are disposed on the outer surface of the hollow cylinder, whereas the center segment is supported on the inner surface of the hollow cylinder. The drive wheel is supported for rotation relative to the hollow cylinder, so that the two hollow cylinders and the drive wheel form a simple gear which transforms the rotation speeds as desired.
The connection of the reflector antenna with the hollow cylinder of the rotor portion embodies an advantageous drive for the reflector antenna. A corresponding drive can be used for controlling two antenna movements in the vertical plane, wherein electrical power is supplied by a wire of the connecting cables.
According to another embodiment of the invention, after the connecting cables exits the channel, the cables s guided to an attachment point of the rotor portion through a tube connected to the drive wheel. The connecting cables is guided in this tube with ample clearance so as to be able to perform a compensating motion conforming to the respective antenna motion.
According to another embodiment of the invention, the tube is bent in the shape of a gallows that is curved from the exit of the channel of the drive wheel towards a rotation point formed on the rotor portion. The connecting cables passes through the rotation point and extends towards a connecting point formed on the rotor portion, with the ends of the connecting cables being connected to the connecting point. The gallows-like shape precisely guides the connecting cables by preventing the cables from leaving a predetermined passageway when the rotor portion rotates. This ensures that the antenna is guided accurately and without error.
According to another embodiment of the invention, the tube is bent in the shape of a gallows that is curved from the exit of the channel of the drive wheel towards an attachment point formed in a guide tube connected with the rotor portion. A strand of the connecting cables that exits from the gallows-shaped tube is guided into the guide tube towards the rotor portion. The guide tube allows the attachment point to be moved to a particularly advantageous location which is preferably located on the rotation axis. This enables simple and space-saving guiding of the connecting cables.
According to another embodiment of the invention, the attachment point of the stator portion is formed as an apex of a dome which is rigidly connected with the stator portion. The connecting cables extends along the walls of the dome from the attachment point to a connecting point. This guide arrangement for the connecting cables is particularly suited for a reflector antenna that is covered by a dome. Guiding the connecting cables along the wall of the dome represents a simple and cost-effective mechanical solution.
According to another embodiment of the invention, the cross-section of the tube is suitable for receiving at least one connecting cables. In this way, the tube can guide several connecting cables between the rotor portion and the stator portion without causing interference between the various connecting cables due to the rotation of the rotor. Likewise, shielded cables that can include an electric power cables for supplying power to the drive can be commonly guided between the rotor portion and the stator portion.
According to another embodiment of the invention, the tube is at least partially formed as a flexible spiral wherein the connecting cables can be guided through the unobstructed cross-section of the spiral. In this way, the tube can be easily adapted to the prevailing conditions between the rotor portion and the stator portion.
According to another embodiment of the invention, the motors can be controlled by a controller, with control signals for a respective vertical and horizontal control of the antenna drives being produced by a comparator circuit. The comparator circuit makes it possible to orient the reflector antenna in a direction where received power optimal.
According to another embodiment of the invention, horizontal and vertical control signals can be produced by a deviation from the largest possible receivable signal. The reflector antenna will thereby always attempt to move to a region of a highest possible received antenna power.
According to another embodiment of the invention, eight control signals can be generated for controlling to a motor that control""s antenna movements in the perpendicular and horizontal direction, wherein the control signal is produced by changes in the received power of the antenna depending on a ship""s motion. In this way, the motor that control the antenna movement in the vertical direction is influenced so as to maintain the reflector antenna always at the most advantageous angular position, where the reflector antenna receives an optimal antenna power, independent of the instantaneous ship movement. This allows for the compensation of the ship""s movement.